Existing cable connection systems and termination systems for connecting a cable to an apparatus are known in the art. A termination system typically includes, at a minimum, a cable or wire, an apparatus, a metallic lug (i.e., a connector typically having a bore in one end for insertion of a cable and an aperture at the opposite end for connection to an apparatus bushing), a stud (i.e., a pin type or threaded device inserted into the aperture of the metallic lug), mating devices (i.e., devices that couple to the stud to maintain the stud within the aperture of the metallic lug) and a housing (i.e., a device that encloses the cable/apparatus connection and forms a tight seal with the outside of the metallic lug, cable shield, insulation, and jacket to prevent contamination or corrosion of the connection).
According to a commonly known termination system, an end of the cable is prepared, prior to termination, by stripping, peeling back or removing all layers surrounding the internal conductive element of the cable including the cable jacket, insulation, shielding, etc., such that the cable conductor is exposed. The cable conductor is then inserted into the bore of a metallic lug, which is crimped (i.e., pressure is applied to the exterior of the metallic lug bore until the cable conductor cannot be easily removed). Thereafter, the metallic lug is inserted into a bore entrance of a housing, sometimes via an interference fit (discussed in greater detail below), such that the end of the metallic lug containing the aperture enters the housing first.
Next, a stud is connected to a first mating device utilizing one of various methods known in the art. Alternatively, the stud may be permanently affixed to the first mating device. Typically, the first mating device is a component affixed to the apparatus (e.g., transformer, high voltage switch, etc.) to be coupled to the cable. A second bore entrance of the housing is then placed over the stud such that the stud penetrates the metallic lug aperture. A second mating device is then inserted into a third bore entrance and coupled to the stud such that a conductive physical connection is created between the metallic lug and the first mating device. The connection of the metallic lug, stud, and mating devices may incorporate additional components and may be performed in alternate configurations utilizing a variety of methods that are known in the art.
Depending on certain criteria, such as the amperage rating of the cable, a metallic lug may be required that has a larger outside diameter than the cable. For example, a 200 ampere connector system is able to use a metallic lug having a smaller outside diameter than the cable. However, a 600 ampere connector system must use a metallic lug having a larger outside diameter than the cable. The 600-ampere metallic lug is larger for a number of reasons, including high momentary current and the need to bolt the 600-ampere metallic lug to the mating device. In addition to its larger diameter, the lug and lug interface is typically longer than that used by the 200 ampere connector system, therefore the 600 ampere connector system requires a longer housing which is more difficult to assemble. Consequently, a connector system that works well for a 200 ampere cable may not be used to terminate a 600 ampere cable unless a cable adapter is provided to adapt the outside diameter of the cable to a diameter larger than the outside diameter of the metallic lug. Unfortunately, the addition of a cable adapter adds time and complexity to the installation of the termination, derates the termination's ampacity (i.e., the termination must be rated at a lower current than the cable on which it is installed), introduces an additional point of potential failure, and requires choosing the correct cable adapter from a range of cable adapter sizes. Therefore, it would be desirable to use a 200 ampere-type termination system to perform a 600-ampere termination without the need to utilize a cable adapter.
Many types of 200 ampere connector systems are in use today. Interference fit tubular connector systems have existed in the prior art for 200 ampere cables for over thirty-five years. Typically, an end of the cable is prepared and the resulting exposed cable conductor is inserted into a metallic lug, an end of which is then crimped to the cable. Thereafter, the metallic lug is inserted into one end of a tubular housing. The inside diameter of the tubular housing is designed to be smaller than the outside diameter of the cable, but larger than the outside diameter of the metallic lug. Therefore, the metallic lug slides easily into the tubular housing. However, the cable must be forced into the tubular housing, causing an interference fit (i.e., insertion of the cable stretches the elastomeric material of the tubular housing such that the tubular housing elastically grips the cable insulation, shield, and jacket creating a secure contact that does not allow moisture, dirt, and/or water to penetrate the seal between the cable and the tubular housing). Whereas interference fit tubular connector systems are commonly used for 200 ampere connections, they are not suitable for 600 ampere systems. This is because the outside diameter of the metallic lug is larger than the outside diameter of the cable, and the metallic lug is longer in length, therefore requiring a longer housing.
Shrinkable tubular connector systems are also commonly used for 200 ampere terminations, since they do not require the relatively high assembly forces required by interference fit connector systems. In lieu of forcing a cable into a housing, a shrinkable connector system incorporates a housing with an inside diameter that is radially expanded to a diameter larger than its intended final diameter, which, similar to the interference fit, is smaller than the outside diameter of the cable to be terminated. Since the inside diameter of the tubular housing is radially expanded, the cable and metallic lug can be easily inserted into the tubular housing without the application of force. When the components are in the proper position, the tubular housing is released from its radially expanded state, or shrunk, to the intended final inside diameter, thereby creating a tight seal with the cable. Many methods of shrinking a housing are known in the art including removal of a retaining member (i.e., a physical device located internal or external to the housing that physically holds the inside diameter of the housing in its radially expanded state) and application of heat, pressure, or chemicals. Conventional shrinkable tubular connector systems are popular, easy to install, and work well with 200 ampere straight connector systems and other connector systems having non-critical geometries. However, they are not suitable for 600 ampere cable terminations due to the different interface and critical geometry associated with a 600 ampere elbow connector system.
For example, a conventional internal retaining member is a core used to radially expand the housing, which is used only with tubular connector systems, such as the 200 ampere straight connector systems. Tubular, straight connector systems can accommodate the core because it allows the core to extend through and out of either end of the connector system. Cores, however, have a flaw. The ends of the core cannot withstand excessive pressure, such as the pressure of the expanded housing, and will collapse if such pressure is applied. Therefore, the core must be longer than the connector system, wherein the ends of the core are external to the housing, at a sufficient distance, ensure that they are not subjected to undue pressure. Accordingly, the expanded housing is usually centered in the middle of the core. In order for the housing to be centered in the middle of the core and permit the ends of the core to extend a sufficient distance outside of the housing, it is necessary for the housing to be tubular. If the core is inserted into a non-tubular connector system, such as a 600 ampere connector system, one end of the core must be within the housing of the connector system. Because of the pressure of the housing, the end of the core within the housing would likely collapse, resulting in the entire core collapsing. External cores encounter similar problems. Therefore, internal and external cores are typically not used with non-tubular connector systems.
As stated above, a typical 600 ampere connector system uses a cable adapter that has one diameter that forms a tight seal with the cable insulation and shield and another diameter that forms a tight seal with the interior of the housing. Although the cable adapter creates many problems, as discussed below, the cable adapter is required because the outside diameter of the metallic lug is larger than the inside diameter of the tubular housing and cannot be easily “pushed” into the tubular housing. If the metallic lug is allowed to touch the inside of the housing, physical damage or contamination of the interior of the tubular housing may occur, both of which could result in an electrical failure of the connector system. In contrast, if the inside diameter of the tubular housing is increased to prevent interference to the outside diameter of the metallic lug, the tubular housing would no longer be able to form a tight seal with the smaller diameter of the cable.
Although the cable adapter allows 600 ampere cables to be connected utilizing the aforementioned housings, the installation of the cable adapter creates many problems. First, for example, choosing the correct cable adapter for the cable insulation diameter size from a range of sizes, the complexity and time required to complete the connection is increased due to the installation of the additional cable adapter component. Second, the cable adapter and its associated two interference fit connections (i.e., connecting the cable to the cable adapter and connecting the cable adapter to the housing) introduce an additional potential point of failure to the resulting cable connection. Third, performing the two interference fit connections associated with the cable adapter increases the amount of labor required to terminate the cable. Fourth, the cable adapter derates the resulting cable connection by creating an air gap between the metallic lug and the housing that acts to thermally insulate the cable. Finally, the cable adapter further derates the system by encircling the cable insulation thereby adding additional thermal insulation to the cable. The magnitude of the combined derating of the termination is such that, in practice, cable systems designed for 1000 amperes may be required to operate at a maximum of 600 amperes.
In order to provide a better understanding of the state of the art related to the field of electrical connector systems, discussed below are several references. Although these references serve to provide a perspective as to the state of the related art, they fail to disclose the novel aspects of the present invention as discussed in detail herein.
For example, U.S. Pat. No. 3,515,798 to Sievert (“Sievert”) discloses a shrinkable, tubular, connector system for performing straight or other non-critical geometry connections using a metallic lug with an outside diameter smaller than the cable. The tubular housing is held in a radially expanded state by a tubular core comprised of a single strip wound helically and welded together such that a tubular core having a consistent inner and outer diameter is formed. After the installer connects the cable, metallic lug, and mating device and inserts the resulting assembly into the housing, the installer pulls the end of the single strip away from the tubular housing causing the tubular core to separate along the helical grooves. When the helical grooves separate, the core loses its tubular configuration and no longer holds the tubular housing in its radially expanded state. The housing thereby shrinks, encircling the cable, metallic lug, and mating device, and creating a tight seal with the cable.
Similar to Sievert, U.S. Pat. No. 3,824,331 to Mixon, Jr. et al. (“Mixon”) also discloses a shrinkable tubular connector system for performing straight or other non-critical geometry connections using a metallic lug with an outside diameter smaller than the cable. Mixon also discloses a core that is located external to the tubular housing. The ends of the tubular housing are rolled backwards onto the external core such that the core holds the rolled portions of the tubular member in position. After the installer connects the cable, metallic lug, and mating device and inserts the resulting assembly into the housing, the installer unrolls the ends of the tubular housing onto the protruding cable. As the ends are unrolled, the tubular housing contracts forming a tight seal with the cable. When the ends are completely unrolled, the external core is removed.
U.S. Pat. No. 6,189,575 to Ions et al. (“the Ions '57 patent”) discloses a recoverable article that may be used as a housing in a shrinkable connector system for performing straight or other noncritical geometry connections using a metallic lug with an outside diameter smaller than the cable. The recoverable article, or housing, comprises an inner member having a plurality of cavities. A holdout structure, similar to the previously discussed cores, holds the tubular housing in a radially expanded state by occupying the cavities on the interior of the tubular housing. After the installer connects the cable, metallic lug, and mating device and inserts the resulting assembly into the housing, the installer releases an initiating member of the holdout structure causing the tubular housing to contract and form a seal with the cable.
U.S. Pat. No. 6,230,746 to Ions et al. (“the Ions '746 patent”) discloses a recoverable article similar to that disclosed in the Ions '575 patent. However, the recoverable article of the Ions '746 patent comprises an inner member having a plurality of channels, not cavities. Therefore, the holdout structure holds the tubular housing in a radially expanded state by occupying the channels on the interior of the tubular housing. After the installer connects the cable, metallic lug, and mating device and inserts the resulting assembly into the tubular housing, the installer pulls the holdout structure from the housing as a single piece causing the tubular housing to contract and form a seal with the cable.
Similar to the Ions '746 patent, U.S. Pat. No. 6,337,440 to Ions et al. (“the Ions '440 patent”) also discloses a recoverable article having an inner member having a plurality of channels. However, whereas the holdout device disclosed in the Ions '746 patent is physically removed, the holdout device disclosed in the Ions '440 patent is mechanically weakened. Therefore, when the installer connects the cable, metallic lug, and mating device and inserts the resulting assembly into the housing, the installer activates the mechanical weakening of the holdout structure causing the tubular housing to contract and form a seal with the cable.
U.S. Pat. No. 5,922,423 to Jeremko (“Jeremko”) also discloses a shrinkable tubular connector system for performing straight or other non-critical geometry connections using a metallic lug with an outside diameter smaller than the cable. More specifically, Jeremko discloses a molded polymeric core located internal to the tubular housing that holds the tubular housing in a radially expanded state. When the tubular housing is ready for shrinking, a tensioning element located at one end of the core is manually manipulated to facilitate removal of the core. According to Jeremko, disclosed is a core that is lighter, less expensive, and easier to manufacture than the cores in use prior to Jeremko.
U.S. Pat. No. 4,070,746 to Evans et al. (“Evans”) discloses a chemically shrinkable tubular connector system for performing straight or other non-critical geometry connections using a metallic lug with an outside diameter smaller than the cable whereby an outer rigid core holds the tubular housing in a radially expanded state. When the installer is ready to shrink the tubular housing, chemical solvents are applied to the outer rigid core destroying its adhesion to the tubular housing. The rigid outer sleeve may then be peeled or broken from the tubular housing, causing the housing to shrink and form a tight seal with the cable.
In contrast to the previously discussed shrinkable tubular connector systems, U.S. Pat. No. 5,421,750 to Crotty (“Crotty”) discloses an interference fit elbow connector system. The system disclosed in Crotty is specifically designed for 200 ampere cables and for terminating a first cable to a selectively removable second cable. A first cable coupled to a metallic lug having an aperture at its end is inserted utilizing an interference fit into one of the three bore entrances of the elbow housing. A second cable coupled to a stud is inserted into a second bore entrance such that the stud engages the aperture of the metallic lug. A threaded connector is then inserted into the third bore entrance and engaged with the stud and rotated until a tight electrical connection is formed between the three components.
U.S. Pat. No. 3,993,387 to Venezia (“Venezia”) discloses a cable connector system that minimizes derating of the termination utilizing two different methods. First, Venezia discloses filling the air gaps between the metallic lug and the housing with an internal shield located around the cable. Second, Venezia discloses a rounded design for both the internal shield and the housing to eliminate any remaining electrical stress resulting from an improper fit between the internal shield and the housing.
Finally, U.S. Pat. No. 3,980,374 to Fallot (“Fallot”) discloses an interference fit connector system comprising two bores affixed at the center of each bore such that the two bores are perpendicular to each other resulting in four bore entrances. The system is specifically designed to connect two 600 ampere primary distribution system cables. The housing receives two cables on opposing ends of one bore. A cable adapter and two interference fits are used for each cable (i.e., to connect the cable to the cable adapter and to connect the cable adapter to the housing).
Cable termination systems that terminate a cable coupled to a metallic lug of a larger diameter than the cable are known in the art. However, these cable termination systems all require the use of a cable adapter to adapt the outside diameter of the cable to a diameter larger than the outside diameter of the metallic lug. The cable adapter creates many problems including additional complexity and time to complete the installation, introduction of an additional point of failure, higher installation forces, derating of the resulting cable termination, and higher cost.
Furthermore, the majority of these systems require the use of a sealing jacket to seal the system housing to the terminated cable. However, the use of a sealing jacket that is separate from the housing introduces an additional point of potential failure of the termination, additional area subject to water or soil penetration, increased installation time and unnecessary installation complexity.
In light of the prior art discussed herein, it is desirable to provide a simple, easy to install, shrinkable cable connector system using a housing having two or more bores and a metallic lug with a larger outside diameter than the cable that does not require a cable adapter, the large installation forces necessary for installation of the cable adapter, or a separate sealing jacket.